The present invention relates to a tooling system for handling optical micro-mechanical devices, and in particular, to a tooling fixture that becomes an integral part of the packaged optical micro-mechanical device.
Fabricating complex micro-electro-mechanical systems (MEMS) and micro-optical-electro-mechanical systems (MOEMS) devices represents a significant advance in micro-mechanical device technology. Presently, micrometer-sized analogs of many macro-scale devices have been made, such as for example hinges, shutters, lenses, mirrors, switches, polarizing devices, and actuators. These devices can be fabricated, for example, using Multi-user MEMS Processing (MUMPs) available from Cronos Integrated Microsystems located at Research Triangle Park, N.C.
One method of forming a MEMS or MOEMS device involves patterning the device in appropriate locations on a substrate. As patterned, the device lies flat on top of the substrate. For example, the hinge plates of a hinge structure or a reflector device are both formed generally coplanar with the surface of the substrate using the MUMPs process. Applications of MEMS and MOEMS devices include, for example, data storage devices, laser scanners, printer heads, magnetic heads, micro-spectrometers, accelerometers, scanning-probe microscopes, near-field optical microscopes, optical scanners, optical modulators, micro-lenses, optical switches, and micro-robotics.
Packaging MEMS devices presents unique problems due to the physically active nature of the microstructures. To maintain a stable environment and to keep out dust particles, corrosive and/or potentially fouling vapors, etc., the micro-machined structures must be enclosed within a sealed package. A sealed package also minimizes the risk of physical damage during handling or operation. Traditional integrated circuit encapsulation methods such as epoxy resin potting and thermoplastic injection molding, while useful with integrated circuits, which have no moving parts, are incapable of use directly with micro-machined structures. The encapsulant must not contact the active portions of the micro-machined structure. Moreover, common encapsulation techniques such as injection molding, often requiring pressures of 1000 psi, would easily crush the microstructure.
One application for micro-machined structures is in connection with processing optical signals, such as optical switches, wavelength specific equalizers, polarization mode dispersion compensators, and the like. These applications, however, require coupling optical fibers with the packaged micro-machined structures. Various techniques are known for packaging MEMS devices, such as disclosed in U.S. Pat. No. 6,146,917 (Zhang et al.) EP0852337; and EP1057779. None of these packaging techniques, however, teach coupling optical fibers to the MEMS device.
The present invention relates to a tooling system for handling optical micro-mechanical devices. A tooling fixture is attached to the MEMS die, preferably before the optical micro-mechanical devices are released. The tooling fixture does not interfere with removal of the sacrificial material, facilitates handling of the MEMS die and ultimately becomes an integral part of the packaged optical micro-mechanical device.
In one embodiment, the package for optical micro-mechanical devices includes a die with one or more optical micro-mechanical devices on a first surface of a substrate. The first surface includes a die reference surface. A tooling fixture is attached to a second surface of the die. The package frame includes an aperture and a package frame reference surface proximate the aperture adapted to receive the die reference surface such that the optical micro-mechanical devices are located in the aperture. One or more optical interconnect alignment mechanisms terminate adjacent to the aperture. Distal ends of one or more optical interconnects are located in the optical interconnect alignment mechanisms and optically coupled with one or more of the optical micro-mechanical devices.
The tooling fixture can be a heat sink, a compliant thermally conductive material and/or a tooling post. A cover seals the tooling fixture to the package frame. In one embodiment, the tooling fixture engages with the cover. In another embodiment, an encapsulating material seals the die and the tooling fixture to the package frame.
One or more contact pads can be interposed between the die reference surface and the package frame reference surface. The contact pads electrically couple one or more optical micro-mechanical devices with external electrical contacts. Alternatively, the contact pads electrically couple one or more optical micro-mechanical devices with a flexible circuit member. The contact pads can also electrically couple one or more optical micro-mechanical devices with contact pads located on the package frame reference surface.
The present invention is also directed to a method of packaging optical micro-mechanical devices. The method includes the steps of preparing a die comprising one or more optical micro-mechanical devices on a first surface of a substrate. The first surface includes a die reference surface. A tooling fixture is attached to a second surface of the substrate. A package frame is prepared including an aperture and a package frame reference surface proximate the aperture adapted to receive the die reference surface such that the optical micro-mechanical devices are located in the aperture. One or more optical interconnect alignment mechanisms are prepared on the package frame. The optical interconnect alignment mechanisms on the package frame are positioned to align with corresponding optical micro-mechanical devices on the die when the die reference surface is engaged with the package frame reference surface. The tooling fixture can be a heat sink, a compliant thermally conductive material and/or a tooling post.
The method includes positioning one or more optical interconnects in the optical interconnect alignment mechanisms on the package frame and engaging the die reference surface with the package frame reference surface to capture the optical interconnects. One or more of the optical interconnects are captured between in the optical interconnect alignment mechanisms on the package frame and the corresponding optical interconnect alignment mechanisms on the die. In one embodiment, the die is sealed to the package frame using an encapsulating material. Another embodiment, a flexible circuit is electrically coupled to the die.
In one embodiment, the step of attaching the tooling fixture occurs before the optical micro-mechanical devices are released from the substrate. In another embodiment, the step of attaching the tooling fixture occurs before the step of preparing the die including the optical micro-mechanical devices.
The die and the tooling fixture can be sealed to the package frame using an encapsulating material. In another embodiment, the die and the tooling fixture are sealed to the package frame using a cover. The tooling fixture can optionally engage with the cover.
The present invention is also directed to an optical communication system including at least one packaged optical micro-mechanical device in accordance with the present invention.